A radio frame in a Long Term Evolution (LTE) system comprises frame structures of a Frequency Division Duplex (FDD) mode and a Time Division Duplex (TDD) mode. FIG. 1 is a schematic diagram of a frame structure in an FDD mode according to the relevant art, as shown in FIG. 1, one radio frame of 10 ms is composed of 20 time slots, wherein the length of each time slot is 0.5 ms and the time slots are numbered from 0 to 19; the time slots 2i and 2i+1 compose a subframe i, the length of which is 1 ms. FIG. 2 is a schematic diagram of a frame structure in a TDD mode according to the relevant art, as shown in FIG. 2, one radio frame of 10 ms consists of two half frames, wherein the length of each half frame is 5 ms; one half frame comprises 5 subframes, wherein the length of each subframe is 1 ms; the subframe i is defined as two time slots 2i and 2i+1, wherein the length of each time slot is 0.5 ms. In the above-mentioned two frame structures, for a normal cyclic prefix (Normal CP), one time slot comprises 7 symbols, wherein the length of each symbol is 66.7 μs, wherein the CP length of the first symbol is 5.21 μs, and the lengths of the rest 6 symbols are 4.69 μs; for an extended cyclic prefix (Extended CP), one time slot comprises 6 symbols, wherein the CP lengths of all the symbols are 16.67 μs.
The release number of LTE corresponds to R8 (Release 8), the release number of the additional release thereof is R9 (Release 9); furthermore, as regards the further LTE-Advance, the release number thereof is R10 (Release 10). Three types of downlink physical control channels are defined in LTE as follows: a physical control format indicator channel (PCFICH), a physical hybrid automatic retransmission request indicator channel (PHICH), and a physical downlink control channel (PDCCH).
The information born by the PCFICH is used for indicating the number of orthogonal frequency division multiplexing (OFDM) symbols for transmitting the PDCCH in a subframe and is sent on the first OFDM symbol of the subframe, wherein the frequency location at which the information is located is determined by a system downlink bandwidth and a cell identify (ID).
The PHICH is used for bearing feedback information about positive acknowledgement/negative acknowledge (ACK/NACK) of uplink transmission data. The number of the PHICH and the position in time-frequency thereof can be determined by a system message and a cell ID in a physical broadcast channel (PBCH) of a downlink carrier where the PHICH is located.
The PDCCH is used for bearing downlink control information (DCI), comprising uplink and downlink scheduling information and uplink power control information. The DCI format is divided into the following types: DCI format 0, DCI format 1, DCI format 1A, DCI format 1B, DCI format 1C, DCI format 1D, DCI format 2, DCI format 2A, DCI format 3, DCI format 3A etc., wherein:
DCI format 0 is used for indicating the scheduling of a physical uplink shared channel (PUSCH);
DCI format 1, DCI format 1A, DCI format 1B, DCI format 1C and DCI format 1D are different modes used for scheduling a PDSCH codon;
DCI format 2, DCI format 2A and DCI format 2B are different modes used for space division multiplexing;
and DCI format 3 and DCI format 3A are different modes used for power control instructions of a physical uplink control channel (PUCCH) and the PUSCH.
A physical resource transmitted by the physical downlink control channel (PDCCH) takes a control channel element (CCE) as a unit, wherein the size of a CCE is 9 resource element groups (REG), i.e. 36 resource elements, and a PDCCH may occupy 1, 2, 4 or 8 CCE(s). As regards the sizes of these four types of PDCCHs occupying 1, 2, 4 or 8 CCE(s), a tree-based aggregation is used, i.e., the PDCCH occupying 1 CCE can start from any one of the CCE location; the PDCCH occupying 2 CCEs starts from the CCE location of an even number; the PDCCH occupying 4 CCEs starts from the CCE location of 4 integer multiple; and the PDCCH occupying 8 CCEs starts from the CCE location of 8 integer multiple.
Each aggregation level defines a search space, comprising a common search space and a user equipment (UE) specific search space. The number of CCEs of the whole search space is determined by the number of OFDM symbols and the number of the groups of the PHICH which are occupied by a control area instructed by the PCFICH in each downlink subframe. The UE performs blind detection on all possible PDCCH code rates in the search space according to the DCI format corresponding to the transmission mode.
In the kth subframe, a control domain bearing the PDCCH is composed a group of CCE, of which the number is NCCE, K numbered from 0 to NCCE, K−1 The UE should detect a group of PDCCH candidates in each non-DRX (non-Discontinuous Reception) subframe so as to obtain control information, and the detection refers to decoding the PDCCH in the group according to all the DCI formats to be detected. The PDCCH candidates required to be detected are defined in a manner of search space, as regards the aggregation level L□{1, 2, 4, 8}, the search space Sk(L) is defined by a group of PDCCH candidates. In the search space Sk(L) the CCE corresponding to the PDCCH candidate m is defined by the following formula:L·{(Yk+m′)mod └NCCE,k/L┘}+i, 
Wherein, as regards the user-specific search space, under the sense that the UE configures a carrier instruction domain, m′=m+M(L)·nCI, wherein nCI is the carrier indication domain value; and under the sense that the UE does not configure a carrier instruction domain, m′=m, wherein m=0, . . . , M(L)−1. M(L) is the number of PDCCH candidates to be detected in the search space Sk(L), i=0, . . . , L−1.
As regards the common search space, Yk=0, L takes 4 and 8.
As regards the UE-Specific search space, L takes 1, 2, 4 and 8.Yk=(A·Yk-1)mod D, 
wherein Y−1=nRNTI≠0, A=39827, D=65537, k=└ns/2┘, ns is a timeslot number in a radio frame. nRNTI is a corresponding RNTI (Radio Network Temporary Identifier).
The UE should detect two common search spaces of which the aggregation levels are 4 and 8 respectively, and four UE-specific search spaces of which the aggregation levels are 1, 2, 4 and 8 respectively, and the common search space can be overlapped with the UE-specific search space. Particular detection time(s) and corresponding search space are as shown in Table 1:
TABLE 1Corresponding relation table between detection times and correspondingsearch spaceSearch space Sk(L)Number ofAggregation levelPDCCHTypeLSize [in CCEs]candidates M(L)UE-specific16621264828162Common41648162
The UE, through high-layer signalling, is semi-statically configured to receive PDSCH data transmission according to the instruction of the PDCCH of the UE-Specific search space based on one of the followings transmission modes:
Mode I: Single antenna port; and port 0
Mode II: Transmit diversity
Mode III: Open-loop spatial multiplexing
Mode IV: Closed-loop spatial multiplexing
Mode V: Multi-user multiple input multiple output (Multi-user MIMO)
Mode VI: Closed-loop Rank=1 precoding
Mode VII: Single antenna port; and port 5
If the UE is configured by a high-layer to use a cyclic redundancy check (CRC) which is scrambled by a cell radio network temporary identifier (C-RNTI) to decode the PDCCH, then the UE should decode the PDCCH and all relevant PDSCHs according to corresponding combinations defined in table 2:
TABLE 2Corresponding relation table of downlink transmission mode, DCI format,search space and PDSCHUEdownlinktransmissionPDSCH transmission planmodeDCI formatSearch spacecorresponding to PDCCHMode IDCI format 1ACommon and C-single antenna port, and port 0RNTI defined UEspecificDCI format 1C-RNTI defined UESingle antenna port, and port 0specificMode IIDCI format 1ACommon and C-Transmission diversityRNTI defined UEspecificDCI format 1C-RNTI defined UETransmission diversityspecificMode IIIDCI format 1ACommon and C-Transmission diversityRNTI defined UEspecificDCI format 2AC-RNTI defined UEOpen-loop spatial multiplexing orspecifictransmission diversityMode IVDCI format 1ACommon and C-Transmission diversityRNTI defined UEspecificDCI format 2C-RNTI defined UEClosed-loop spatial multiplexing orspecifictransmission diversityMode VDCI format 1ACommon and C-Transmission diversityRNTI definedspecificDCI format 1AC-RNTI UE definedMultiuser multiple input multipleUE specificoutputMode VIDCI format 1ACommon and C-Transmission diversityRNTI defined UEspecificDCI format IBC-RNTI defined UEClosed-loop Rank = 1 precodingspecificMode VIIDCI format 1ACommon and C-if the number of the antenna ports of theRNTI defined UEPBCH is 1, using single antenna port,specificand port 0, otherwise, using transmitdiversityDCI format 1C-RNTI defined UEsingle antenna port; and port 5specificMode VIIIDCI format 1ACommon and C-if the number of the antenna ports of theRNTI defined UEPBCH is 1, using single antenna port,specificand port 0, otherwise, using transmitdiversityDCI format 2BC-RNTI defined UEDual-layer transmission, and port 7 andspecific8; or single antenna port, and port 7 and8Mode □DCI format 1ACommon and C-if the number of the antenna ports of theRNTI defined UEPBCH is 1, using single antenna port,specificand port 0, otherwise, using transmitdiversityDCI format 2CC-RNTI defined UEUp to 8 layer transmission, and port 7-specific14
Since an LTE-Advanced network requires to be able to access an LTE user, an operation frequency band thereof requires to cover the current LTE frequency band, there is no distributable spectral bandwidth of continuous 100 MHz on this frequency band, a direct technique required to be solved for the LTE-Advanced is using the carrier aggregation technique to aggregate several continuous component carrier frequencies (frequency spectrum) distributed at different frequency bands so as to form a 100 MHz bandwidth which is able to be used by the LTE-Advanced. That is to say, the aggregated frequency spectrum is divided into n component carrier frequencies (frequency spectrum), the frequency spectrum in each component carrier frequency (frequency spectrum) being continuous.
In the further release Release 11 of the LTE-Advanced, since the requirements of the user for accessing increase, the original physical downlink control channel PDCCH resource is not to sufficiently meet the requirements of the new release, FIG. 3 is the schematic diagram illustrating configurations of PDCCH and PDSCH in a subframe in the relevant art, as shown in FIG. 3, it is possible that the limit of the number of the PDCCH symbols will be unable to meet the effect brought by the increase of the users. Meanwhile, under the scene of heterogeneous networks, since different types of eNodeBs have relatively strong interference, the problem of macro eNodeB interfering with micro eNodeB (Pico) and the problem of home eNodeB interfering with macro eNodeB require to be well solved. Then developing a new PDCCH resource is to be an effective solution for solving the above-mentioned problems. FIG. 4 is a contrast schematic diagram of time-frequency locations of the PDCCH in the relevant art and the possible time-frequency locations of the new PDCCH, the new PDCCH can be mapped on 2 time slots of the subframe, or, the new PDCCH is only mapped on part of continuous OFDM symbols, as shown in FIG. 4, the legacy (existing) PDCCH and the new PDCCH exist on a resource block in parallel.
However, it only specifies in relevant art that the method for sending the legacy PDCCH is, for each aggregation level, sending downlink control information on continuous control channel elements, but the manner is relatively single, especially, the new PDCCH takes a physical resource block as a channel element, if the new PDCCH is only mapped on the continuous physical resource blocks, then the new PDCCH would be unable to obtain the diversity gain, and for the UE at the edge of a cell having a relatively poor channel condition, a stable transmission performance is not able to be obtained.
As regards the relatively single manner for sending the physical downlink control information in relevant art, no effective solution has been proposed so far.